Forward-looking: A Finnish startup has secured $7.6 million Euro ($8.2 million) in seed funding to scale up its unique sand battery technology. The money will be used to grow the company's sales and R&D teams, and help advance the tech's capabilities. But what exactly is a sand battery, anyway?
A sand battery uses sand or sand-like material as a medium to store energy as heat. Its core purpose is to serve as a high-capacity reservoir for surplus wind and solar energy. The unit consists of an insulated silo filled with sand, and is outfitted with heat transfer pipes and tech to convert electricity to heat. When needed, heat can be extracted from the system for a variety of uses.
The system doesn't rely on exotic materials, either. The company said sand grain size isn't all that important, and they prefer to use materials that aren't typically used in the construction industry.
Polar Night Energy installed its first sand battery in Vatajankoski's district heating network in Kankaanpää, Finland, which went into service in 2022. That battery affords 100 kW of heating power and 8 MWh of capacity.
Last month, Polar Night Energy announced it had partnered with Finnish district heating company Loviisan Lämpö to build an industrial-scale sand battery in Pornainen. The unit will measure approximately 13 meters (42.7 feet) high and 15 meters (49.2 feet) wide, and will take a little over a year to construct and test.
Once operational, the bigger battery will be able to store up to 100 MWh of thermal energy and provide 1 MW of heating power. In Pornainen, that'll translate to a full week of heat supply in the winter and nearly a month's worth during the summer.
The sand inside the battery can be heated to more than 1,000 degrees Celsius and is typically limited by the heat resistance of the materials used in construction of the storage facility. Polar Night Energy said its storage system can even be built underground, ideal for regions where real estate is highly valued.
